Memory B cells are a B cell sub-type that are formed within germinal centers following primary infection and are important in generating an accelerated and more robust antibody-mediated immune response in the case of re-infection.

Now there is an accumulation of cells of a single clone population which expresses many of the one same type of antibody and that these memory B cells survive for long periods of time in a body.

Disregarding the number of different cells applying for one and the same antibody, how many Memory B cells are there in average humans which relate to different antibodies?